English: In 1849 Robert Stevenson's son Alan and John Rennie's son, Sir John, were involved in an acrimonious exchange of letters which were reprinted in the Civil Engineer & Architect's Journal concerning who "designed and built" the Bell Rock Lighthouse. This illustration was submitted by Alan Stevenson to demonstrate his father's priority. However the illustration clearly shows Rennie's influence in the shaping of the tower up to the high water level. This was the one influence he himself claimed, never going as far as his son. How far his many letters influenced Stevenson is less easy to determine.